Fire Tests

Cables have to be properly designed, manufactured and also tested

Many tests are carried out during manufacturing or as final inspections. Many of them are attended by customers or third part inspectors. You can find here the main tests concerning the behaviour of cables under fire conditions.

Constructive Standards

BS 7629-1:2008 Electric Cables

Specification for 300/500 V fire resistant screened cables having low emission of smoke and corrosive gases when affected by fire. Multicore and multipair cables.

This standard includes the currently most common cable onto the market of the fire resistant cables. Those cables are used in fire alarm and emergency lighting applications. They have a rated voltage of 300/500 V.
Generally, the cables are particularly flexible and easy to be installed.

These standards require that the cables get through the fire resistance tests prescribed by BS 6387 standards.

BS 7846:2009 Electric Cables

Thermosetting insulated, armoured, fire-resistant cables of rated voltage 600/1000V, having low emission of smoke and corrosive gases when affected by fire.
Specification.

This Standard refers to the armoured cables with rated volt- age 600/1000 V.

The circuit integrity performance under fire conditions is assessed on the basis of various tests which either separately measure resistance to fire, resistance to fire with water, and resistance to fire with mechanical shock, or in combination measure resistance to fire with mechanical shock and water.

BS EN 60702-1:2002 Mineral Insulated Cables

Their terminations with a rated voltage not exceeding 750 V Cables. These standards apply to mineral insulated cables. Those cables have an insulation completely different from those seen so far: they are extremely resistant but rigid. Their installation is not handy and a particular care has to be paid to the installation, to prevent moisture absorption by the mineral oxide.

BS EN 50200

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Fire Resistance

This test is carried out to verify the circuit integrity of cables exposed to fire at 830oC and mechanical shocks.

Classification
PH 15 – flame exposure for 15 min
PH 30 – flame exposure for 30 min
PH 60 – flame exposure for 60 min
PH 90 – flame exposure for 90 min
PH 120 – flame exposure for 120 min

BS EN 50200 Annex E (Standard Cable – BS 5839-1 – Clause 26.2d)

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Fire Resistance

This test is carried out to verify circuit integrity during a fire. The cable is exposed to a flame at 830°C and mechanical shocks for 15 minutes and additional 15 minutes to flame, mechanical shocks and water spray.

BS 8434-2 (Enhanced Cable – BS 5839-1 – Clause 26.2e)
fp-standards003Fire Resistance

This test is carried out to verify circuit integrity during a fire. The cable is exposed to a flame at 930°C and mechanical shocks for 60 minutes and additional 60 minutes to flame, mechanical shocks and water spray.

Fire Tests

BS 6387

Following tests are carried out to verify if a cable is capable of maintaining circuit integrity under fire condition, fire with water, and fire with mechanical shocks. During the tests the cables are maintained at their rated voltage.

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Fire Resistance (Cat. A B C S)

The cable is exposed to fire at the specified temperature and time.

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Fire and Water Resistance (Cat. W)

The cable is exposed for 15 minutes to flame at 650°C and for additional 15 minutes to fire and water spray

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Fire Resistance with Mechanical Shocks (Cat. X Y Z)

The cable is mounted on a vertical panel and shocked with a steel bar for 15 minutes while submitted to the action of a flame.

Performance Table
TestCategory
Fire Resistance
650℃ for 3 hoursA
750℃ for 3 hoursB
950℃ for 3 hoursC
950℃ for 20 minutesS
Resistance to Fire and Water
650℃W
Resistance to Fire with Mechanical Shock
650℃X
750℃Y
950℃Z
See our Fire Performance Video Library.
IEC 60331
fp-standards004Fire Resistance

This test is carried out to verify circuit integrity even during a fire. A sample of cable is held on a flame at about 750°C for a period of minimum 90 min, under rated voltage. No break or short circuit should occur. The test can also be performed in more severe conditions, up to 1100°C. Fibre optic cables can be tested in same conditions, monitoring the attenuation of the signal of one or more fibres.

Classification

CEI 20-36/2-1 – IEC 60331-21 – Electrical cables up to 0,6/1 kV
CEI 20-36/2-3 – IEC 60331-23 – Data cables
CEI 20-36/2-5 – IEC 60331-25 – Fibre optic cables

BS EN 60332-3, IEC 60332-3

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Samples of cables 3.5 m long in quantities required by standard are installed on a ladder inside a metallic cabinet. They are subjected to the action of a flame at 750°C for a specific time (20 or 40 minutes). Cables must not burn for more than 2.5m.

BS EN 60332-1, IEC 60332-1 BS EN 60332-2, IEC 60332-2 for small diameter cables

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Flame Propagation Test on a Single Cable

A 60 cm long sample of cable is vertically fixed with two clamps inside a small cabin, open on the front. The cable is subjected to the action of a flame produced by a calibrated Bunsen burner. The application time of the flame is according to the cable diame- ter (60-480 seconds). At the end of the test the burnt portion of cable must not be 50 mm close to the higher clamp.

 

Toxicity Tests

BS EN 50267-2-1, IEC 60754-1

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HCI Emission

Each non metallic material of the cable (-1.0g) is burnt into a tube furnace up to 800°C. A controlled air flow rate absorbs the generated gases in an appropriate solution. The tritation of the solution allows to determine the developed hydrochloric acid (HCI) amount.

Standard: BS EN, 50267-2-1, IEC 60754-1, CEI 20-37/2-1
Required values: ≤ 0.5% HCI

BS EN 50267-2-2, IEC 60754-2

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Smoke Corrosivity

This test allows estimation of corrosiveness against metals of gases released when cables burn. Materials composing the cable are burnt into a tubular oven with a temperature higher than 935°C. A controlled air flow rate absorbs the generated gases in a specific distilled water solution. pH and conductivity are finally measured.

Standard                     Required values
BS EN 50267-2-2,       pH ≥ 4,3
IEC 60754-2,               Conductivity
CEI 20-37/2-2              ≤ 100 µS.cm-1

BS EN 61034-2, IEC 61034-2
Smoke Density

In a 3 m cube metal cabinet, samples of cables are burned by 100 cm3 of alcohol contained in a metal tray. A photometric system is based on a light source and a photocell placed horizontally in
the mid vertical plane of the cube, at height of 2.15 m. Absorbance or light transmission are measured.

Standard EN 61034-2, IEC 61034-2, CEI 20-37/3 (Transmittance – LT)

 

Required values ≥ 60%

 

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